laptop computer supply for heaters

[Andy Le Blanc]

I was looking at the PS to me putor and had the notion that one might be able to use it as a regulated DC supply for tube heaters.

Its modular, and doesn't take a lot space... 18.5v 3.5A

I figured 3 6v fil. in series .... don't forget to balance (match) the current thru each tube with small value R parallel with the heater

just might be worth a try... old power adapters are like tribbles

[Garthhog]

Don't you need to double the heater voltage when running them DC (12.6VDC vs 6.3VAC)? I could be confused...

[David Root]

No. You can use 6.3V DC instead of AC, no problem.

Personally I'd stay with parallel heaters, but a lot of old TVs used series wired heaters.

[Phil_S]

I've often wondered about this. I dunno about 18V and 3 tubes per unit, but certainly 12V supplies are plentiful and pairs seem to be the charm as I don't think you'd need to be so concerned about balancing if it's a pair of the same tube type. You might need an extra unused one in the preamp section.

[JMFahey]

If voltage matches and current available is enough, yes, it will work.

To put some numbers into it, a 12A*7 needs 6.3V , 300mA , DC or AC , so 3 in series would add up to 19V (what many laptop supplies can offer) and most "bricks"can put out around 2.5A , so there's way more than enough.

Only problem is that being an SMPS derived voltage, and not meant to be used "raw" but re-reconverted into whatever the notebook may need, designers don't care that much about digital/switching "noise" and some background "hash" might get in the preamp, specially if high gain.

That said, there is a chip amp kit specially designed to use a laptop supply, they first regulate the around 18 to 20V typical supply down to very clean and stable 12V, and then feed the chipamp with it.

Probably the same can be done for heaters, wiring each 12A*7 for 12V , 150 mA .

[roberto]

I suggest you to put it outside the chassis, and to prefilter the supply before going to the heaters.

[Cameron]

I was looking at the PS to me putor and had the notion that one might be able to use it as a regulated DC supply for tube heaters.

Its modular, and doesn't take a lot space... 18.5v 3.5A

I figured 3 6v fil. in series .... don't forget to balance (match) the current thru each tube with small value R parallel with the heater

just might be worth a try... old power adapters are like tribbles

Yes you can ....you may have to add some small filtering to get rid of some of the switching high pitched noise ....but yes it works good.

[Leo_Gnardo]

How about that current surge before the filaments come up to temperature. Will the 'puter supply choke on that?

Tribbles are trouble. Feed 'em kibble & watch 'em double.